"One
of the reasons—besides sheer artistry—that Katinka
Matson's work resonates so strongly with us is that is that the
insect-like vision that results from scanning direct-to-CCD runs
so much deeper in us than vision as processed through a lens. By
removing the lens, Matson's work bypasses an entire stack of added
layers and takes us back to when we saw more by looking
at less." — George Dyson

Science
is a kind of open laboratory for a democracy. It's a way to experiment
with the ideals of our democratic societies. For example, in science
you must accept the fact that you live in a community that makes
the ultimate judgment as to the worth of your work. But at the same
time, everybody's judgment is his or her own. The ethics of the community
require that you argue for what you believe and that you try as hard
as you can to get results to test your hunches, but you have to be
honest in reporting the results, whatever they are. You have the
freedom and independence to do whatever you want, as long as in the
end you accept the judgment of the community. Good science comes
from the collision of contradictory ideas, from conflict, from people
trying to do better than their teachers did, and I think here we
have a model for what a democratic society is about. There's a great
strength in our democratic way of life, and science is at the root
of it.

LEE
SMOLIN, a theoretical physicist, is concerned with quantum gravity,
"the name we give to the theory that unifies all the physics
now under construction." More specifically, he is a co-inventor of
an approach called loop quantum gravity. In 2001, he became a founding
member and research physicist of the Perimeter Institute for Theoretical
Physics, in Waterloo, Ontario. Smolin is the author of The Life
of The Cosmos and Three Roads to Quantum Gravity.

"In
the year Dolly was born, 1996, scientists and technologists
celebrated the centenary of JJ Thompson's discovery of the
electron. If civilisation survives until 2096, what anniversary
will then attract more attention: the electron's bicentenary?
Or Dolly's centenary?" — Martin Rees

Dolly
1996 - 2003

REMEMBERING
DOLLY [2.14.03]

Dolly,
the first clone from a mammal, died on
February 13th at the age of 6 years old.

Where were you on July 5, 1996? What did you think when you read the
news about the accomplishment of Ian
Wilmut and his team at Roslyn Institute in Edinburgh? What is Dolly's
lasting historical significance? How does Dolly's life change our view
of humanity?

Contributors:
Jaron Lanier, Martin Rees, John Horgan, Robert Sapolsky

"One
of the reasons—besides sheer artistry—that
Katinka Matson's work resonates so strongly with us is
that is that the insect-like vision that results from scanning
direct-to-CCD runs so much deeper in us than vision as
processed through a lens. By removing the lens, Katinka's
work bypasses an entire stack of added layers and takes
us back to when we saw more by looking at less." — George
Dyson

George
Dyson Visual processing (in humans and other organisms)
is characterized by layers: not only the layers in the
retina, behind the retina, in the visual cortex, and finally
in our consciousness and our culture as we interpret the
ultimate results. There are also evolutionary layers, and
the lensless, scanner-like visual system of the insect
still lingers, unseen but essential, in some of those layers
between light and brain.

One of the reasons—besides
sheer artistry—that Katinka Matson's work resonates
so strongly with us is that is that the insect-like vision
that results from scanning direct-to-CCD runs so much deeper
in us than vision as processed through a lens. By removing
the lens, Katinka's work bypasses an entire stack of added
layers and takes us back to when we saw more by
looking at less.

George
B. Dyson
Science historian
Author of Darwin Among the Machines and Project Orion: The
True Story of the Atomic Spaceship.

William
Calvin There would seem to be two perceptual-level
things operating that make Katinka Matson's scanner images
look so different: 1) the lighting fades with distance
into black, and 2) scanning one line at a time with a moving
light source off to the side means that a sheen develops
on the flower surfaces, that adds to the unusual 3-D effect.
It is somewhat like wearing a headlamp in a dark room and
rotating a vase of flowers in your hands, back and forth.

On the cognitive level, new perceptual ways of looking at things can
provide categorization challenges. Sometimes the result is confusion,
other times it is a window to creativity. Being forced to take a nonstandard
view of familiar things is why Stan Ulam used to say that he considered
the use of rhyme in poetry to be a stimulus to creativity, as it forced
you not to use the familiar first-choice word but to instead keep searching
through all the near synonyms for one that rhymes, and so help you
find better words to fit with the other ones.

"When
I was a boy I felt that the role of rhyme in poetry was
to compel one to find the unobvious because of the necessity
of finding a word which rhymes. This forces novel associations
and almost guarantees deviations from routine chains or
trains of thought. It becomes paradoxically a sort of automatic
mechanism of originality.... And what we call talent or
perhaps genius itself depends to a large extent on the
ability to use one's memory properly to find the analogies...
essential to the development of new ideas."

William
H. Calvin
Affiliate Professor of Psychiatry and Behavioral Sciences
University of Washington, Seattle
Author of A Brain for All Seasons: Human Evolution and Abrupt
Climate Change and the Atlantic Monthly's cover story,
"The great climate flip-flop."

I'll
say nothing to take away from the originality of Katinka's
pictures (which I think are stunning). But it's worth noting
(Katinka and I have talked about this) that a photographic
technique—photogravure—which produces similar
results to the flat bed scanner was in use more than a
hundred years ago, and was exploited to remarkable effect
for photographing plants by Karl Blossfeldt. Some of the
illustrations from his 1928 book, Art Forms in Nature,
are reproduced at the website below. The parallels to Katinka's
pictures are striking.

My
own interest, as a psychologist concerned with aesthetics,
is as much in the content as in the technique of the Blossfeldt/Matson
pictures. Why flowers and plants? Why do
human beings take such a delight in the visual rhymes and
contrasts exemplified by these "natural art forms". I proposed
my own theory thirty years ago, in a paper called "The
Illusion of Beauty", giving a rather different answer
to the one Bill Calvin cites from Stanislaw Ulam. Here's
a brief extract (which includes a discussion of "rhymes
in nature"):

From
The "Illusion of Beauty" (p. 36 on)

[People's
delight in discovering 'rhyme' finds echoes in another
remarkable aspect of human behaviour: the passion for collecting. ]
In an essay called "The reflex of purpose" Pavlov characterised
collecting as "the aspiration to gather together the
parts or units of a great whole or of an enormous classification,
usually unattainable", and went on: "If we consider
collecting in all its variations, it is impossible
not to be struck with the fact that on account of this
passion there are accumulated often completely trivial
and worthless things, which represent absolutely no
value from any point of view other than the gratification
of the propensity to collect. Notwithstanding the worthlessness
of the goal, every one is aware of the energy, the
occasional unlimited self-sacrifice, with which the
collector achieves his purpose. He may become a laughing-stock,
a butt of ridicule, a criminal, he may suppress his
fundamental needs, all for the sake of his collection" (Pavlov,
1928).

Collecting,
though its practitioners are not usually credited with
aesthetic sensitivity, is not, I believe, far removed
from the appreciation of beauty. Consider for a moment
the nature of a typical collection, say a stamp collection.
Postage stamps are, in structuralist terms, like man
made flowers: they are divided into 'species', of which
the distinctive feature is the country of origin, while
within each species there exists tantalising variation.
The stamp collector sets to work to classify them.
He arranges his stamps in an album, a page for the
species of each country. The stamps on each page 'rhyme'
with each other, while they contrast with those on
other pages.

But
Pavlov was right: stamp collecting is a worthless activity.
As we have moved through my examples, from an infant
animal learning to recognise the objects in the world
about him, to a child learning to name pictures in
a book, to a man sticking stamps in an album, we have
moved further and further from activities which have
any obvious biological function. They are all, I submit,
examples of the propensity to classify, but with each
example the classification seems to have less and less
direct survival value. We
should not be surprised. Earlier, I compared the pleasure
people get from classification with the pleasure they
get from sexual activity. Now, though sex has a clear
biological function, it goes without saying that not
every particular example of sexual activity has in
fact to be biologically relevant to be enjoyable. Indeed,
much human sexual activity takes place at times when
the woman, for natural or artificial reasons, is most
unlikely to conceive. And so too the process of classification
may give pleasure in its own right even when divorced
from its proper biological context. Once Nature had
set up people's brains the way she has, certain 'unintended'
consequences followed-and we are in several ways the
beneficiaries.

So
let me turn, at last, to beauty—to examples of
rhyme and contrast which people deem aesthetically
attractive. I want first to consider not 'works of
art' but certain natural phenomena which people call
beautiful and yet which have no 'natural' value to
us.Among
the wealth of examples of beauty in nature, I shall
choose the case of flowers, flowers have an almost
universal appeal, to people of all cultures, all classes,
and all ages. We grow them in gardens, decorate our
houses and our bodies with them, and above all value
them as features of the natural landscape. They are
regarded indeed as paragons of natural beauty, and
I believe it is no accident that they are so admired,
for in at least three ways flowers are the embodiment
of 'visual rhyme'.

Consider
first the static form of a simple flower such as a
buttercup or daisy. The flower-head consists of a set
of petals arranged in radial symmetry around a cluster
of stamenss, and the flower-head is carried on a stalk
which bears a set of leaves. Petals, stamens, and leaves
form three sets of contrasting rhyming elements: each
petal differs in detail from the other members of its
class yet shares their distinctive shape and colour,
and the same is true for the stamens and the leaves;
the features that serve to unite each set serve at
the same time to separate one set from another. Second,
consider the flower's kinetic form. The living flower
is in a continual state of growth, changing its form
from day to day. The transformations which occur as
the flower buds, blossoms, and decays give rise to
a temporal structure in which each successive form
rhymes with the preceding one.

Third,
consider groups of flowers. Typically each flowering
plant bears several blooms, and plants of the same
species tend to grow in close proximity, so that we
are presented with a variety of related blooms on show
together. But, more than this, groups of flowers of
different species commonly grow alongside one another—daisies
and buttercups beside each other in the field, violets
and primroses together in the hedgerow. Thus while
the flowers of one species rhyme with each other the
rhyme is given added poignancy by the contrasting rhymes
of different species.

It
is this last aspect that perhaps more than anything
makes flowers so special to us. The flowers of different
species are of necessity perceptually distinct in colour,
form, and smell in order that they may command the
loyalty of pollinating insects. People neither eat
their pollen nor collect their nectar, yet flowers
provide us with a kind of nourishment—food for
our minds, ideally suited to satisfy our hunger for
classification.

But
flowers have no monopoly of natural beauty. In fact
almost wherever we come across organic forms we discover
the structure of visual rhyme. Long before architects
invented the module, Nature employed a similar design
principle, basing her living creations on the principle
of replication-at one level replication of structural
elements within a single body, and at another replication
of the body of the organism as a whole. But, at either
level, the replicas are seldom, if ever, perfect copies:
in the leaves of a tree, the spots of a leopard, the
bodies of a flight of geese, we are presented with
sets of 'variations on a theme'. And it is not only
among living things we find such structures, for inanimate
objects too tend to be shaped by physical forces into
'modular' forms—mountain peaks, pebbles on a
beach, clouds, raindrops, ocean waves—each alike
but different from the others. Thus, through its varied
but coherent structure, a natural landscape can match
the rhythmic beauty of a gothic church. Or of a musical
symphony.

Nicholas Humphrey
Theoretical Psychologist
School Professor at the London School of Economics
Professor of Psychology at the New School for Social Research
Author of Consciousness Regained, The Inner Eye, A History
of the Mind, and The Mind Made Flesh

UNIVERSES
(Continued)

LOOP
QUANTUM GRAVITY: LEE SMOLIN[2.24.03]

(Lee Smolin:) Several
years ago, I had the chance to move to Imperial
College in London with the possibility of starting
a research group. After I had been there a while,
someone came to see me and said,"I represent some
people who want to start an institute for theoretical
physics. They want it to do fundamental work in
things like quantum gravity, string theory, cosmology,
and quantum mechanics and they have at least $100
million. What would you do? What fields would be
included? How would you structure it? Who would
be good to hire? Would you have a director? Would
you pick somebody honored and wise and give him
all the power to structure it, or would you just
hire a bunch of young people out of graduate school
and give it to them on a high-tech entrepreneurial
model and let them run with it?" We talked about
this, and he also talked to many people in these
fields—Fotini Markopoulou-Kalamara, Carlo
Rovelli, Chris Isham, Roger Penrose, and many others.

Very
important in these discussions was the structure.
My view was that it's wrong to give one person
all the power, because this is science, and science
functions best when people are independent and
there's a community. The proposed institute—the
Perimeter Institute for Theoretical Physics, in
Waterloo, just outside of Toronto—was particularly
meant to be an incubator for innovative ideas about
fundamental questions, and new ideas tend either
to come from young people or from people who keep
themselves young by constantly moving into new
areas. We scientists constantly criticize each
other, and we work best in an open atmosphere where
anybody can criticize anybody, honestly and directly.
You also want a supportive atmosphere, where people
are generous and sympathetic about difficulties
and failures. We talked about all these things,
and over time the prospect began to look more attractive
than staying in London.

The
inventor of the idea, and the chief donor to the
Perimeter Institute, is Michael Lazaridis, who
is co-chief executive of Research in Motion, the
company that makes Blackberries. He and the board
he created made it clear that what they wanted,
structurally, was something like the Institute
for Advanced Study, in Princeton. They set the
mandate, they set the framework, but they are not
involved in day-to-day issues of scientific direction
and hiring. Mike is absolutely essential, but he's
never come to us and said, "I think you have to
hire this person" or "I think that that's
not a good direction to go in." One thing they
did very early was to create a committee of prominent
scientists as advisors, to oversee what we do.
They're there to see that we don't wander off in
strange directions scientifically—to keep
us honest.

We're
now in a funky old building in Waterloo which used
to be a restaurant; my office is next to the old
bar. There's a wonderful atmosphere; people love
it. Construction has started on a new building
designed by two fantastic young architects from
Montreal, Gilles Saucier and Andre Perrotte. At
the beginning of the process, we traveled with
them to Cambridge and London, where people have
recently built buildings for physicists and mathematicians,
and talked about what works, what doesn't work,
and why. I believe that our building is going to
be a better place to do theoretical physics than
anything that exists now. We already are said by
some to be the hot place in two fields—quantum
gravity and quantum information theory. We opened
in September 2001, which was a strange time to
begin any endeavor, starting with three scientists
on long term appointments; Robert Myers, Fotini
Markopoulou, and myself—a string theorist
and two people in quantum gravity. Very much present
in our minds from the beginning was the idea that
we were not going to favor one particular approach.
We have good people in both camps, and we are creating
an atmosphere where people in different camps will
talk to each other. A lot of good science has happened
so far. We hired two very good people in quantum
theory: Lucien Hardy, from Oxford, who has done
exciting work in foundations of quantum theory
and quantum information theory; and Daniel Gottesman,
a young star of quantum information theory. In
2002, we had ten postdocs, several visitors, lots
of people coming and going. In June, the Canadian
prime minister and the minister of industry visited
and pledged more than $25 million to our support.
The deputy provincial minister of Ontario also
came and pledged at least $11 million. It was heartening
to see that the leaders of at least one country
understand that the support of pure science is
essential for a modern democracy.

Science
is a kind of open laboratory for a democracy. It's
a way to experiment with the ideals of our democratic
societies. For example, in science you must accept
the fact that you live in a community that makes
the ultimate judgment as to the worth of your work.
But at the same time, everybody's judgment is his
or her own. The ethics of the community require
that you argue for what you believe and that you
try as hard as you can to get results to test your
hunches, but you have to be honest in reporting
the results, whatever they are. You have the freedom
and independence to do whatever you want, as long
as in the end you accept the judgment of the community.
Good science comes from the collision of contradictory
ideas, from conflict, from people trying to do
better than their teachers did, and I think here
we have a model for what a democratic society is
about. There's a great strength in our democratic
way of life, and science is at the root of it.

Now
I want to talk about the problem of quantum gravity
and the two best developed approaches that have
been proposed to solve it, which are called loop
quantum gravity and string theory. This is a case
in which different people have taken different
approaches to solving a fundamental scientific
problem, and there are interesting lessons to be
learned from how these theories have developed
since the early 1980s—lessons about space
and time and also about how science works.

Quantum
gravity is the name we give to the theory that
unifies all of physics. The roots of it are in
Einstein's general theory of relativity and in
quantum theory. Einstein's general theory of relativity
is a theory of space, time, and gravity; while
quantum theory describes everything else that exists
in the universe, including elementary particles,
nuclei, atoms, and chemistry. These two theories
were invented in the early twentieth century, and
their ascension marked the overthrow of the previous
theory, which was Newtonian mechanics. They are
the primary legacies of twentieth-century physics.
The problem of unifying them is the main open problem
in physics left for us to solve in this century.

Nature
is a unity. This pen is made of atoms and it
falls in the earth's gravitational field. Hence
there must be one framework, one law of nature
of which these two theories are different aspects.
It would be absurd if there were two irreconcilable
laws of physics, one for one domain of the world
and another for another domain. Even in 1915 Einstein
was aware of the issue, and in his very first paper
about gravitational waves, he mentions the paradox
of how to fit relativity together with the quantum.

It's
only since the middle 1980s that real progress
began to be made on unifying relativity and quantum
theory. The turning point was the invention of
not one but two approaches: loop quantum gravity
and string theory.Since then, we have been
making steady progress on both of these approaches.
In each case, we are able to do calculations that
predict surprising new phenomena. Still, we are
not done. Neither is yet in final form; there are
still things to understand. But the really important
news is that there is now a real chance of doing
experiments that will test the new predictions
of these theories.

This
is important, because we're in the uncomfortable
situation of having two well-developed candidates
for the quantum theory of gravity. We need to reduce
these to one theory. We can do this either by finding
that one is wrong and the other right, or by finding
that the two theories can themselves be unified.
(Of course, the result of testing the theories
could be that both of them are eliminated, but
this would be progress, too.)

Until
a few years ago, the situation was very different.
We didn't know how to test the theories we were
working so hard to construct. Indeed, for a whole
scientific generation—that is, since the
middle 1970s—fundamental physics has been
in a crisis, because it has not been possible to
subject our theoretical speculations to experimental
test. This was because the new phenomena that our
theories of quantum gravity predict occur at scales
of energy many orders of magnitude greater than
what can be created in the laboratory—even
in the huge particle accelerators. The scale where
quantum physics and gravity come together is called
the Planck scale, and it is some fifteen orders
of magnitude higher in energy than the largest
accelerators now under construction.

In
quantum theory, distance is inverse to energy,
because you need particles of very high energy
to probe very short distances. The inverse of the
Planck energy is the Planck length. It is where
the classical picture of space as smooth and continuous
is predicted by our theories to break down, and
it is some twenty powers of ten smaller than an
atomic nucleus. Because the Planck scale is so
remote from experiment, people began to put great
trust in mathematics and theory. There were even
some string theorists who said silly things like "From
Galileo to 1984 was the period of modern physics,
where we checked our theories experimentally. Since
then, we work in the age of postmodern physics,
in which mathematical consistency suffices to demonstrate
the correctness of our theories and experiment
is neither possible nor necessary. "I'm not
exaggerating; people really said things like this.

The
idea that you could do experiments to test the
quantum theory of gravity was mentioned from time
to time by a few people through the 1990s, but
to our shame we ignored them. One person who proposed
the idea forcefully is a young man in Rome called
Giovanni Amelino-Camelia. He just ignored everybody
who said, "You'll never probe scales that
small. You'll never test these theories." He told
himself that there must be a way, and he examined
many different possible experiments, looking for
ways that effects of quantum gravity could appear.
And he found them. Now we know more than half a
dozen different experiments we can do to test different
hypotheses about physics at the Planck scale. Indeed,
in the last year, several proposals about Planck
scale physics have been ruled out by experiment.

The
key thing that Amelino-Camelia and others realized
is that we can use the universe itself as an experimental
device to probe the Planck scale. There are three
different ways the universe gives us experimental
probes of the Planck scale. First, there are accelerators
in distant galaxies that produce particles with
energies much higher than we can produce in even
the largest human-made accelerators. Some of these
ultra-high-energy cosmic rays have been observed
hitting our atmosphere with energies more than
10 million times those we have ever produced. These
provide us with a set of ready-made experiments,
because on their way to us they have traveled great
distances through the radiation and matter that
fill the universe. Indeed, there are already surprises
in the data which, if they hold up, can be interpreted
as due to effects of quantum gravity.

Second,
we detect light and particles that have traveled
billions of light years on their way across the
universe to us. During the billions of years they
travel, very small effects due to quantum gravity
can be amplified to the point that we can detect
them.

Finally,
the postulated inflation by which the universe
expanded very rapidly at early times serves as
a kind of microscope, blowing up Planck scale features
to astronomical scales, where we can see them in
small fluctuations in the cosmic microwave radiation.

So
what are the theories we will be testing with these
effects? One is loop quantum gravity.

Loop
quantum gravity started in the early 1980s with
some discoveries about classical general relativity
by Amitaba Sen, then a postdoc at the University
of Maryland. These were made into a beautiful reformulation
of Einstein's theory by Abhay Ashtekar, then at
Syracuse University and now director of the Center
for Gravitational Physics at Penn State—a
reformulation that brought the mathematical and
conceptual language we use to describe space and
time closer to the language used in particle physics
and quantum physics. My colleague Ted Jacobson
of the University of Maryland and I then found
in 1986 that we could use this new formalism of
Ashtekar's to get real results about quantum spacetime.
Since the 1950s, the key equation of quantum gravity
has been one called the Wheeler-DeWitt equation.
Bryce DeWitt and John Wheeler wrote it down, but
in all the time since then, no one had been able
to solve it. We found we could solve it exactly,
and in fact we found an infinite number of exact
solutions. They revealed a microscopic structure
to the geometry of space and told us that space,
at the Planck scale, looks like a network with
discrete edges joined into graphs. The next year,
I was joined by Carlo Rovelli (now of the Centre
de Physique Théorique in Marseille), and
we were able to make a full-fledged quantum theory
of gravity out of these solutions. This became
loop quantum gravity. We were quickly joined by
many others, and now it is a rather large field
of research.

Loop
quantum gravity differs from other approaches to
quantum gravity, such as string theory, in that
apart from using Ashtekar's formalism we made no
modifications to the principles of relativity and
quantum theory. These principles are well tested
by experiment, and our theory is based on their
consistent unification, nothing more. Our approach
joins relativity in the world as we see it, with
three spatial dimensions and matter more or less
as we see it, with quantum mechanics more or less
in the form presented to us by Paul Dirac, Werner
Heisenberg, and their friends. While most people
had given up and were seeking to modify the principles
of either relativity or quantum theory, we surprised
ourselves (and many other people) by succeeding
in putting them together without modifying their
principles.

This
has led to a detailed theory that gives us a new
picture of the nature of space and time as they
appear when probed at the Planck scale. The most
surprising aspect of this picture is that on that
scale, space is not continuous but made up ofdiscrete
elements. There is a smallest unit of space: Its
minimum volume is given roughly by the cube of
the Planck length (which is 10-33 cm).A
surface dividing one region of space from another
has an area that comes in discrete units, the smallest
of which is roughly the Planck length squared.
Thus, if you take a volume of space and measure
it to very fine precision, you discover that the
volume can't be just anything. It has to fall into
some discrete series of numbers, just like the
energy of an electron in an atom. And just as in
the case of the energy levels of atoms, we can
calculate the discrete areas and volumes from the
theory.

When
we first worked out the predictions for these smallest
units of area and volume, we had no idea that they
would be observable in real experiments in our
lifetime. However, a number of people—beginning
with Rodolfo Gambini, of the University of the
Republic in Montevideo, and Jorge Pullin, then
at Penn State—showed that there are indeed
observable consequences. At about the same time,
Amelino-Camelia and others were pointing out that
if there were such effects, they would be detectable
in experiments involving cosmic rays and gamma-ray
bursts. These effects are caused by light scattering
off the discrete structure of the quantum geometry,
analogous to diffraction and refraction from light
scattering off the molecules of the air or liquid
it passes through. The quantum gravity effect is
tiny—many orders of magnitude smaller than
that due to matter. However, we observe light from
gamma-ray bursts—huge explosions, possibly
caused by mergers of binary neutron stars or black
holes—that has traveled across the universe
for some 10 billion light-years. Over such long
distances, the small effects amplify to the point
where they can be observed. Because elementary
particles travel as waves in quantum theory, the
same thing happens to such particles—protons
and neutrinos, for example. It is possible that
these effects may be responsible for the surprises
I mentioned in the observations of very-high-energy
cosmic rays.

Now,
here is the really interesting part: Some of the
effects predicted by the theory appear to be in
conflict with one of the principles of Einstein's special theory
of relativity, the theory that says that the speed
of light is a universal constant. It's the same
for all photons, and it is independent of the motion
of the sender or observer.

How
is this possible, if that theory is itself based
on the principles of relativity? The principle
of the constancy of the speed of light is part
of special relativity, but we quantized Einstein's
general theory of relativity. Because Einstein's
special theory is only a kind of approximation
to his general theory, we can implement the principles
of the latter but find modifications to the former.
And this is what seems to be happening!

So
Gambini, Pullin, and others calculated how light
travels in a quantum geometry and found that the
theory predicts that the speed of light has a small
dependence on energy. Photons of higher energy
travel slightly slower than low-energy photons.
The effect is very small, but it amplifies over
time. Two photons produced by a gamma-ray burst
10 billion years ago, one redder and one bluer,
should arrive on Earth at slightly different times.
The time delay predicted by the theory is large
enough to be detectable by a new gamma-ray observatory
called GLAST (for Gamma-ray Large Area Space Telescope),
which is scheduled for launch into orbit in 2006.
We very much look forward to the announcement of
the results, as they will be testing a prediction
of a quantum theory of gravity.

A
very exciting question we are now wrestling with
is, How drastically shall we be forced to modify
Einstein's special theory of relativity if the
predicted effect is observed? The most severe possibility
is that the principle of relativity simply fails.
The principle of relativity basically means that
velocity is relative and there is no absolute meaning
to being at rest. To contradict this would mean
that after all there is a preferred notion of rest
in the universe. This, in turn, would mean that
velocity and speed are absolute quantities. It
would reverse 400 years of physics and take us
back before Galileo enunciated the principle that
velocity is relative. While the principle may have
been approximately true, we have been confronting
the frightening possibility that the principle
fails when quantum gravity effects are taken into
account.

Recently,
people have understood that this possibility appears
to be ruled out by experiments that have already
been done: that is, if the principle of relativity
fails when quantum gravity effects are taken into
account, effects would already have been seen in
certain very delicate measurements involving atomic
clocks and in certain astrophysical processes involving
supernova remnants. These effects are not seen,
so this drastic possibility seems less likely.
So a hypothesis about the structure of space and
time on scales twenty orders of magnitude smaller
than an atomic nucleus has been ruled out by experiment!

But
there is another possibility. This is that the
principle of relativity is preserved, but Einstein's
special theory of relativity requires modification
so as to allow photons to have a speed that depends
on energy. The most shocking thing I have learned
in the last year is that this is a real possibility.
A photon can have an energy-dependent speed without
violating the principle of relativity! This was
understood a few years ago by Amelino Camelia.
I got involved in this issue through work I did
with João Magueijo, a very talented young
cosmologist at Imperial College, London. During
the two years I spent working there, João
kept coming to me and bugging me with this problem.
His reason for asking was that he had realized
that if the speed of light could change according
to conditions—for example, when the universe
was very hot and dense—you might get an alternative
cosmological theory. He and Andreas Albrecht (and
before them John Moffat) had found that if the
speed of light was higher in the early universe,
you get an alternative to inflationary cosmology
that explains everything inflation does, without
some of the baggage.

These
ideas all seemed crazy to me, and for a long time
I didn't get it. I was sure it was wrong! But João
kept bugging me and slowly I realized that they
had a point. We have since written several papers
together showing how Einstein's postulates may
be modified to give a new version of special relativity
in which the speed of light can depend on energy.

Meanwhile,
in the last few years there have been some important
new results concerning loop quantum gravity. One
is that the entropy of a black hole can be computed,
and it comes out exactly right. Jacob Bekenstein
found in his PhD thesis in 1971 that every black
hole must have an entropy proportional to the area
of its horizon, the surface beyond which light
cannot escape. Stephen Hawking then refined this
by showing that the constant of proportionality
must be, in units in which area is measured by
the Planck length squared, exactly one quarter.
A challenge for all quantum theories of gravity
since then has been to reproduce this result. Moreover,
entropy is supposed to correspond to a measure
of information: It counts how many bits of information
may be missing in a particular observation. So
if a black hole has entropy, one has to answer
the question, What is the information that the
entropy of a black hole counts?

Loop
quantum gravity answers these questions by giving
a detailed description of the microscopic structure
of the horizon of a black hole. This is based on
the atomic description of spatial geometry, which
implies that the area of a black hole horizon is
quantized—just as space is, it is made up
of discrete units. It turns out that a horizon
can have, for each quantized unit of area, a finite
number of states. Counting them, we get exactly
Bekenstein's result, with the one quarter.

This
is a very recent result. When we first did this
kind of calculation, in the mid-1990s, we got the
entropy right up to an overall constant. A few
months ago, in a brilliant paper, Olaf Dreyer,
a postdoc at the Perimeter Institute, found a very
simple and original argument that fixes that constant,
using a completely classical property of black
holes. He uses an old argument of Neils Bohr called
the correspondence principle, which tells us how
to tie together classical and quantum descriptions
of the same system. Once the constant is fixed,
it gives the right entropy for all black holes.

Another
big development of loop quantum gravity is that
we now know how to describe not only space but
spacetime—including causality, light cones,
and so on—in loop quantum gravity. Spacetime
also turns out to be discrete, described by a structure
called a spin foam. Recently there have been important
results showing that dynamical calculations in
spin-foam models come out finite. Together these
two results strongly suggest that loop quantum
gravity is giving us sensible answers to questions
about the nature of space and time on the shortest
scales.

Let
me now say something about string theory, which
is the other approach to quantum gravity that has
been well studied.

String
theory is a very beautiful subject. It attempts
to unify gravity with the other forces by postulating
that all particles and forces arise from the vibrations
of extended objects. These include one-dimensional
objects (hence the name "strings"), but there
are also higher-dimensional extended objects that
go by the name of "branes" (for generalizations
of membranes). String theory comes from the observation
that all the quanta that carry the known forces,
and all the known particles, can be found among
the vibrations of these extended objects.

String
theory is not a complete quantum theory of gravity,
for reasons I'll come to in a minute, but it does
work to a certain extent. It gives, to a certain
order of approximation, sensible predictions for
some quantum gravity effects. These include the
scattering of gravitons (quanta of gravity analogous
to photons) with other particles. For certain very
limited kinds of black holes (actually, not real
black holes but systems with properties similar
to certain special black holes), it gives predictions
that agree with the results of Bekenstein and Hawking.
And it does succeed in unifying gravity with the
other forces.

However
there is some fine print. For string theory to
work, we need to hypothesize that there are six
or seven unobservable dimensions of space. We must
also hypothesize that there are new kinds of symmetries
called supersymmetries, which have not so far been
observed. These symmetries tie together particles
usually considered constituents of matter (like
quarks and electrons) with the quanta of forces
(like photons and gluons).

Supersymmetry
is a beautiful idea—and, indeed, it stands
independent of string theory as an intriguing conjecture
about the elementary particles. Unfortunately,
it is not observed. Were it observed directly,
then for every particle there would be a supersymmetric
partner, which is a partner with the same mass
and the same charges and interactions but a spin
differing by one- half. This is certainly not observed!
If supersymmetry is true, then it is realized in
nature only indirectly; we say, in physicist talk,
that the symmetry is broken. Another way to say
this is that the forces have a symmetry, but the
state of the world does not obey it. (For example,
looking around your living room, you see that the
fact that space has three dimensional symmetry
is broken by the effects of the gravitational field,
which points down.)

There
is some indirect evidence that some people take
as an indication that supersymmetry is present
and will be seen in future experiments in accelerators.
But so far no direct evidence for supersymmetry
has been found. Nor has there been any experimental
evidence for the extra dimensions that string theory
requires.

The
interesting—and unfortunate—upshot
of this is that in the absence of experimental
check, different communities of people have focused
on different questions and invented different imaginary
worlds. Those who work on loop quantum gravity
still live in the world we see, where space has
three dimensions and there is no need for more
symmetries than are observed. Many string theorists
live—at least, imaginatively—in a universe
that has ten or eleven dimensions. A standard joke
is that a string theorist hearing a talk about
loop quantum gravity says, "That's a very
beautiful theory, but it has two big faults: Space
only has three dimensions and there is no supersymmetry!" To
which the speaker replies, "You mean, just
like the real world?" Actually this is not a joke—I've
heard it. (And, by the way, if the world does have
higher dimensions and supersymmetry, that could
be incorporated into loop quantum gravity.)

The
extent to which people can invent imaginary worlds
when science gets decoupled from experiment is
quite extraordinary. They follow a certain aesthetic
of mathematical elegance out there as far as it
takes them. If you buy all that—the extra
dimensions and symmetries and so forth—string
theory does succeed to a certain limited approximation
in unifying gravity and quantum theory. However,
even if it's right, string theory can be only an
approximation to the real theory. One reason is
that there turns out to be an enormous number of
string theories. And so far, while many of them
have been studied, no single string theory has
been discovered that agrees with all the observations
of our universe. There are three features of the
world that no string theory can so far reproduce:
the absence of supersymmetry at low energies, the
presence of a cosmological constant with positive
sign (more on this later), and the complete absence
of a certain kind of field—called a massless
scalar field—that string theories predict
in abundance. Thus it seems likely that even if
string theory is true in some generalized sense,
the actual theory describing our universe must
differ significantly from all string theories so
far invented.

Another
reason that string theory cannot be the final word
is that in string theory one studies strings moving
in a fixed classical spacetime. Thus, string theory
is what we call a background-dependent approach.
It means that one defines the strings as moving
in a fixed space and time. This may be a useful
approximation, but it cannot be the fundamental
theory. One of the fundamental discoveries of Einstein
is that there is no fixed background. The
very geometry of space and time is a dynamical
system that evolves in time. The experimental observations
that energy leaks from binary pulsars in the form
of gravitational waves—at the rate predicted
by general relativity to the unprecedented accuracy
of eleven decimal places—tells us that there
is no more a fixed background of spacetime geometry
than there are fixed crystal spheres holding the
planets up. The fundamental theory must unify quantum
theory with a completely dynamical description
of space and time. It must be what we call a background-independent
theory. Loop quantum gravity is such a one; string
theory is not.

The
debate between proponents of background-dependent
and background independent theories is in fact
just the modern version of an ancient debate. Since
the Greeks, the argument has raged between those
who believed that space and time have an eternally
fixed, absolute character and those who thought
space and time are no more than relations between
events that themselves evolve in time. Plato, Aristotle,
and Newton were absolutists. Heraclites, Democritus,
Leibniz, Mach, and Einstein were relationalists.
When we demand that the quantum theory of gravity
be background-independent, we are saying we believe
that the triumph that general relativity represented
for the relational point of view is final and will
not be reversed.

Much
of the argument between string and loop theorists
is a continuation of this debate. Most string theorists
were trained as elementary-particle physicists
and worked their whole lives in a single fixed
spacetime. Many of them have never even heard of
the relational/absolute debate, which is the basic
historical and philosophical context for Einstein's
work. Most people who work in loop quantum gravity
do so because at some point in their education
they understood the relational, dynamical character
of spacetime as described in general relativity,
and they believe in it. They don't work on string
theory because they cannot take seriously any candidate
for a quantum theory of gravity that is background-dependent
and hence loses (or at best hides) the relational,
dynamical character of space and time.

Similarly,
at first string theorists were resistant to the
idea that the fundamental theory must be background-independent.
However, I think that by now almost all string
theorists have come around. They did so because
there are reasons internal to string theory to
believe that the fundamental theory must be background-independent.
This is because string theory turned out to be
non-unique. While the original hope, back in the
1980s, was that mathematical consistency would
suffice to determine the unified theory, it turns
out that in fact there are a huge number of equally
consistent string theories. Each is as consistent
as any other and each depends on a different choice
of fixed background. Further, in spite of the huge
numbers of string theories we know about, none
of them agree with observations on the three points
I mentioned above.

As
a result, in a move called "the second string
revolution" in the middle 1990s, string theorists
postulated that all the different string theories
so far discovered plus an infinite number of so-far-undiscovered
theories are but approximations to one unified
theory. This theory has been called M theory, but
there is no general agreement as to what its principles
are or what mathematical form it takes. The idea
is that M theory, if it exists, would be background-independent
and have all the different background-dependent
string theories as different solutions to it.

Many
string theorists now say that the main problem
in string theory is to find M theory and give string
theory a background-independent form. But the funny
thing is that not many string theorists have tried
to work on this problem. The problem is that all
their intuition and tools are based on background-dependent
theories. When I bother string theorists about
this, they tell me it's premature—not time
to work on this problem yet.

I've
had a lot of interesting conversations with the
leaders of string theory—Edward Witten, Leonard
Susskind, Renate Kallosh, David Gross, John Schwarz,
Michael Green, Andrew Strominger, and many others.
We clearly disagree about methodology. They tell
me I have the wrong idea about how science works.
They tell me one cannot hope to solve fundamental
problems by attacking them directly. Instead one
must follow the theory where it goes. A leading
string theorist has said to me several times that "I
learned a long time ago that string theory is smarter
than I am" and that to try to tell the theory where
to go would be to presume that you are "smarter
than the theory." Another tells me that string
theory works because it is "a very disciplined
community" in which the leaders impose an order
on the community of researchers to insure that
only a few problems are worked on at any one time.

I
have huge respect for the string theorists as people
and for what they have accomplished. Some of them
are good friends. At the same time, I think they're
wrong about how science works. I certainly don't
want to say that I'm smarter than string theory,
or than string theorists. But I disagree about
the methodology, because I'm sure that fundamental
scientific problems are not solved in such an accidental
way. Einstein used to complain that many scientists
limit themselves to easy problems—"drilling
where the wood is thin," as he put it. On one of
the few occasions when I talked to Richard Feynman,
he said that many theoretical physicists spend
their careers asking questions that are only of
mathematical interest. "If you want to discover
something significant," he told me, "only
work on questions whose answers will lead to new
experimental predictions."

I
also learned from the philosopher Paul Feyerabend
the importance of conflict and pluralism in science.
I read him in graduate school and I felt imediately
that, unlike other philosophers I had been reading,
he really understood what we scientists actually
do. He pointed out that science often develops
out of the tension that arises when competing research
programs collide. He advised that in such situations
one should always work on the weakest part of each
of the competing programs. He also emphasized that
pluralism in science is good, not bad. According
to him, and I agree, science moves fastest when
there are several healthy competing approaches
to a problem, and stagnates when there is only
one approach. I think this is true on every level—in
the scientific community as a whole, in a research
center or group, and even in each one of us.

So
while I disagree with the leading string theorists
about methodology, this hasn't kept me from working
on string theory. After all, they don't own it;
its open problems are there for anyone to try to
solve. So I decided a few years ago to ignore their
advice and try to construct the background independent
form of M theory. In the process of inventing loop
quantum gravity, we gained a lot of knowledge about
how to make quantum theories of space and time
that are background-independent. We have a mathematical
language, we have a conceptual language, we know
what questions to ask, and we know how to do calculations.
It turns out that there is a lot of loop quantum
gravity that can be generalized and extended by
adding extra dimensions and extra symmetries in
order to make it a suitable language for M theory.

At
first some of my friends and collaborators were
shocked that I was working on string theory. However,
I had an idea that maybe string theory and loop
quantum gravity were different sides of the same
theory, much like the parable of the blind men
and the elephant. I spent about two years working
on string and M theory, with the goal of making
them background-independent and thus unifying string
theory and loop quantum gravity. I did find some
very interesting results. I was able to build a
possible background-independent formulation of
string theory.

The
most interesting results I found use some beautiful
mathematics, having to do with a kind of number
called an octonion. These are numbers that you
can divide, but they fail to satisfy the other
rules, such as commutativity and associativity.
Feza Gürsey, from Yale University and his
students, especially Murat Gunyadin, have for years
been exploring the idea that the octonions might
be connected to string theory. Using octonions,
I was able to develop an attractive idea (from
Corrine Manogue and Tevian Dray of Oregon State
University) that explains why space may look three-dimensional
while being, in a certain mathematical sense, nine-dimensional.
I don't know if the direction I took is right,
but I did find that it is indeed not so hard to
use background-independent methods to formulate
and study conjectures about what M theory is.

Working
on string theory using the methods from loop quantum
gravity was a lot of fun. I was out there with
just a few friends, as it had been in the early
days of loop quantum gravity, and I made real progress.
However, in the last year I put this work aside
because of the new experimental developments. As
soon as I understood what Giovanni Amelino-Camelia
was saying, I realized that this was science and
that's what we had to focus on. Since then, it's
been a lot harder to wake up and go to work in
the morning to an imaginary world with six or seven
extra dimensions.

There
was another piece of shocking news from the experimenters
that took me away from string theory—the
discovery over the last couple of years that most
of the energy in the universe is in a form that
Einstein called the cosmological constant.. The
cosmological constant can be interpreted as indicating
that empty space has a certain intrinsic energy
density. This is a hard thing to believe in, but
the cosmological data cannot now be explained convincingly
unless one assumes that most of the energy of the
universe is in this form. The problem is that string
theory seems to be incompatible with a world in
which a cosmological constant has a positive sign,
which is what the observations indicate. This is
a problem that string theorists are thinking and
worrying very hard about. They are resourceful
people, and maybe they'll solve it; but as things
stand at the moment, string theory appears to be
incompatible with that observation.

Meanwhile,
loop quantum gravity incorporates a positive cosmological
constant extremely well. In fact it's our best
case: If there's a cosmological constant, we're
able find a candidate for the quantum state of
the universe and show that it predicts that the
universe at large scales is governed by general
relativity and quantum theory. So in the last several
months, I've mostly been studying how to make predictions
about the new experiments from a version of loop
quantum gravity that incorporates a positive cosmological
constant.

The good thing about science is that you get these
shocks from the real world. You can live for a few
years in an imaginary world, but in the end the task
of science is to explain what we observe. Then you
look in the mirror and ask yourself, "Do I want
to be out there in eleven dimensions, playing with
beautiful math, when the experiments start coming
in?"

REMEMBERING
DOLLY [2.14.03]

Dolly,
the first clone from a mammal, died on February 13th at the
age of 6 years old.

Where were you on July 5, 1996? What did you think when you read the news about
the accomplishment of Ian Wilmut and
his team at Roslyn Institute in Edinburgh? What is Dolly's lasting historical
significance? How does Dolly's life change our view of humanity?

Dolly,
you were born at the most optimistic moment imaginable. A
world of peace and plenty seemed to be at hand. The major
conflicts of the world suddenly ended or seemed to be on
their way to unforeseen early resolution. These included
the Cold War, Apartheid, even the Middle East conflict. A
global wealth boom was in the works. A new generation of
utopian thinking with a digital flavor had just entered the
mainstream.

Then
you showed up. You were both an inspiration and a challenge.
Like all advances in human capability, your existence would
undoubtedly bring not only healing and happiness, but also
some degree of violence and misery, since that has always
been the nature of human affairs. But what would the balance
be?

In
your short life we have seen humanity, your enabling species,
flunk a series of major tests. A boom brought about by new
productivity tools was distorted into an occasion for fraud
and theft by the accounting and financial industries. What
a shame that good natured good times turned out to be such
an inspiration for white collar criminals. Meanwhile, the
apparent worldwide trend towards peace and reconciliation
abruptly reversed into an awful nexus of hatred, including
even an innovative doctrine of mass suicidal religiosity.

Oh
Dolly, let's hope we have many second chances, and that your
legacy will recall the world as it was at the start of your
life more than what it has come to be at the end of your
life.

In
the year Dolly was born, 1996, scientists and technologists
celebrated the centenary of JJ Thompson's discovery of the
electron. If civilisation survives until 2096, what anniversary
will then attract more attention: the electron's bicentenary?
Or Dolly's centenary?

Ever
since Dolly's birth, I've been puzzled by why so many people
are so upset at the prospect of reproduction by cloning. One
apparent source of concern is that cloning would significantly
reduce the element of chance involved in reproduction. This
view enshrines the genetic shuffling that occurs as a result
of sexual conception as an inviolable mystery, the essence
of life. Certainly sexual recombination has played a vital
creative role in evolution; without it, we wouldn't be here.

But
if randomness per se were an intrinsic good, the ideal procreative
act would be a drunken one-night stand involving a leaky condom.
No one opposes such ancient rituals of romance as courtship
and marriage, which have made mating a less random, more deliberate
process. And only hard-core religious fundamentalists object
to modern medical advances such as contraceptives and genetic
testing, which have reduced the number of babies who are born
unwanted and unhealthy.

All
the silly scenarios in which megalomaniacs make Mini-Me's suggest
that people would only resort to reproductive cloning for scurrilous
selfish motives. First of all, children have always served
as projections of their parents' narcissism. Moreover, those
who seek children through extraordinary means—whether
adoption, in vitro fertilization, or cloning—will arguably
be at least as committed to the responsibilities of parenthood
as those who simply copulate and let the chips fall where they
may.

We
should all be frightened by the prospect of the state controlling
reproduction, as Nazi Germany and other countries—including
the U.S.—did during the heyday of the eugenics movement
early in the last century. But I don't see the harm in allowing
citizens to resort to technologies such as cloning, if they
can afford it, and if cloning is refined so that clones are
not at higher risk of disease (a big if).

A hypothetical: Let's say that a husband and wife whose new-born
daughter has died of sudden-death syndrome want to clone her.
We may find their decision irrational and morbid, but these judgements
are not sufficient to warrant the drastic step of prohibiting
the couple from carrying out their hearts' desire. Where's the
harm?